Fiber length measurements from tapered beards were disclosed by Hertel in the 1940's. Hertel employed the term “amount” (A) to refer to the amount (that is, number or linear density) of fibers in tapered beards and developed what he termed “fibrograms,” which are plots of “amount” as a function of distance from a needle sampler. Hertel worked out the theory for analyzing fibrograms and developed apparatus and methods for length measurements from the 1930s to the 1950s. In particular, Hertel disclosed the determination of a length-distribution curve based on optical analysis. See, as examples, Hertel U.S. Pat. Nos. 2,299,983, 2,404,708 and 3,057,019. For convenience, we refer herein to the result of this measurement method, as well as the method itself, as Lo, meaning length by optical analysis.
A needle sampler for forming tapered beards and employing rotary motions is disclosed in Shofner et al U.S. Pat. No. 6,598,267, titled “Fiber Length and Strength Measurement System,” the entire disclosure of which is hereby expressly incorporated by reference. The disclosed apparatus uses optical extinction, and may also be referred to as an Lo method. In addition, the apparatus disclosed in U.S. Pat. No. 6,598,267 employs air flow resistance to measure the amount versus distance response. We refer herein to length measured by air flow resistance, as well as the method, as La.
The terminologies complete fiber length distribution, fiber length histogram, and fiber length probability density function (PDF) are interchangeably used herein and in the literature on fiber length measurements.
Cotton fiber length measurements (Classer's Staple, 2.5% Span, Upper Half Mean, etc., and Short Fiber Content, etc.) are among the most important descriptors of fiber quality. They strongly correlate with spinning process costs and yarn and fabric qualities. Accordingly, these and related data products strongly impact commercial market values of cotton. It is important that the measurement, or classification, of the qualities be correct, widely understood, and accepted for commercial trading by all parties concerned.
The market has historically caused producers to favor varieties having greater Long Fiber Content (LFC) when all other things, notably pounds per acre yield, are comparable. Reasonably satisfactory LFC measurements are available and widely used in commerce. On the other hand, satisfactory Short Fiber Content (SFC) measurements are not available, despite numerous complaints, primarily from parties in the mill, merchandizing and research segments, which refer to the “rising short fiber content” problem. Current market forces are increasingly causing producers and ginners to favor processing equipment and methods which minimize damage and preserve the length qualities of the fibers, thus minimizing SFC. Accordingly, correct measures of SFC are needed.
The best measure of fiber damage, both in the gins and in the mills, and of spinning performance in the mills, is SFC, either by number or by weight. Only with correct and widely accepted SFC data can producers and designers and operators of processing machinery evaluate the quality of their work and, thereby, realize the financial incentives to improve.
Commercial market forces which are driving all parties concerned to higher (or at least stable) LFCs and lower SFCs are thus also driving the needs for correct, commercially-useful measurements. This means scientifically basic, accurate, precise, rapid and cost-effective measurement of both long fiber content LFC and short fiber content SFC. It follows further that the most basic and best methods provide direct measurement of the complete fiber length distribution, or probability density function (PDF), since all fiber length data products can be derived therefrom.
Current High Volume Instruments (HVI) provide LFC data products, such as Upper Half Mean Length (UHM) or Mean Length (ML), satisfactorily for commercial purposes, along with other fiber quality measurements such as strength (or tenacity), micronaire, color and trash. Such instruments are manufactured by Uster Technologies, Knoxville, Tenn.; Premier Technologies, Coimbatore, India; Lintronics, Haifa, Israel; and Schaffner Technologies, Knoxville, Tenn., with which the present inventors are associated. Current HVI methods however do not provide adequate measurements of the shortest fibers, for several fundamental reasons relating to both sample preparation and tapered beard “amount” (A) measurement. Consequently, current HVI does not provide the complete fiber length distribution and only provides inferential measures of SFC.
The Advanced Fiber Information System (AFIS) also manufactured by Uster Technologies (for an example see the disclosure of Shofner et al U.S. Pat. No. 5,270,787 titled “Electro-Optical Methods and Apparatus for High Speed, Multivariate Measurement Of Individual Entities In Fiber Or Other Samples”), and Suter-Webb array, methods can provide complete fiber length distributions or PDFs. These methods are known to be too expensive, imprecise, or slow for high volume testing. It is also known that AFIS, as a consequence of its rather aggressive opening to produce single fibers, breaks fibers, thus leading to increased SFC and decreased LFC, thus biasing the length data products.
Since new length methods are needed, primarily for commercial trade, it follows that the most preferable methods would be also be compatible with next generation HVI, along with improvements in other fiber quality measurements, such as strength, micronaire, color and trash.